Colias
Colias is a genus of butterflies in the family Pieridae. They are often called clouded yellows in the Palearctic and sulphurs in North America. The closest living relative is the genus Zerene, which is sometimes included in Colias.
This genus occurs throughout the Holarctic, including the arctic regions. They are also found in South America, Africa, China and India. Their caterpillars feed on certain Fabaceae, for example vetches. The adults forage for nectar. most are thus beneficial by keeping weeds at bay, some occasionally become nuisance pests on crops like alfalfa. In some species, the wings of males have brilliant ultraviolet reflection, while those of females do not. Adults of both sexes have various colour forms. Males are particularly conservative based on their genitalia structures. These structures are difficult to identify making it difficult to classify the Colias.
Most if not all species of this genus, as usual for Coliadinae, do not sequester toxins or other noxious compounds from their food plants. They are therefore a well-loved prey item of insectivores as compared to Pieris of the related Pierinae. They make up this disadvantage by being more nimble and better able to evade attacks by would-be predators.
Notable lepidopterologists who did many studies on this genus included Julius Röber, J. Malcolm Fawcett, George B. Johnson and Henry Rowland-Brown.
Systematics
Hybridization runs rampant in these polytypic and clinal butterflies, confounding molecular phylogenetics studies. In general, cladistic analyses of only one type of data cannot be considered reliable. Regardless, the evolutionary distance within some "species" is so large that cryptic speciation rather than interbreeding seems to be the cause. For example, the Beringian populations traditionally assigned to the northern clouded yellow could warrant recognition as a species; hybridization between North American and Asian populations seems to have played a role in their evolution, but as a whole they appear to be a rather old and distinct lineage.
Thermoregulation
Colias are behavioral thermoregulators. They will move their habitats in order to regulate their body temperature. This leads to them having specific and narrow temperature ranges that they could live in. This leaves the Colias to be extremely vulnerable to climate change. The degree of melanism on their wings and fur thickness are major parts of their thermoregulation. The wing absorption/melanization is determined by the proportions of their coloration. They are in a class of pollinators that require minimum fuel due to their small size. When they need pollen they are attracted to flower patterns in the ultraviolet, similar to themselves.
Flight
Colias spend most of their time in active flight and are very strong flyers. Flying is essential for them mate as well as pollinate. But they are very susceptible to temperature and have flight restrictions based on their body temperature. Flight activity is restricted between 27-40 degrees Celsius. Their flight performance is best once at 33-38 degrees Celsius. In order to maintain these temperatures the Colias will use a lateral basking posture. When they reach a temperature outside of the flight activity zone, Colias will find a shaded area under plants in order to cool down.
Species
The genus Colias has approximately 90 different species. It is often difficult to find differences between the species, since they are mostly identified through their wing structure and pattern.Listed alphabetically:Colias adelaidae Verhulst, 1991Colias aegidii Verhulst, 1990Colias alfacariensis Ribbe, 1905 – Berger's clouded yellowColias alexandra W. H. Edwards, 1863 – Queen Alexandra's sulphur, Alexandra sulfur, or ultraviolet sulfurColias alpherakii Staudinger, 1882Colias aquilonaris Grum-Grshimailo, 1899Colias arida Alphéraky, 1889Colias audre Colias aurorina Herrich-Schäffer, 1850 – Greek clouded butterfly or dawn clouded yellowColias baeckeri Kotzsch, 1930Colias behrii W. H. Edwards, 1866 – Behr's sulphur or Sierra green sulfur Colias berylla Fawcett, 1904 – Everest clouded yellowColias canadensis Ferris, 1982 – Canada sulphurColias caucasica Staudinger, 1871 – Balkan clouded yellowColias chippewa W. H. Edwards, 1872 – heath sulphurColias chlorocoma Christoph, 1888Colias christina W. H. Edwards, 1863 – Christina sulphurColias christophi Grum-Grshimailo, 1885Colias chrysotheme – lesser clouded yellowColias cocandica Erschoff, 1874Colias croceus – dark clouded yellow or common clouded yellowColias dimera Doubleday, 1847 – dimera sulphurColias diva Grum-Grshimailo, 1891Colias dubia Fawcett, 1906 – dwarf clouded yellowColias electo – African clouded yellowColias elegans Schultz, 1904Colias elis Strecker, 1885 Colias eogene C. & R. Felder, 1865 – fiery clouded yellowColias erate – eastern pale clouded yellowColias erschoffi Alphéraky, 1881Colias eurytheme Boisduval, 1852 – orange sulphur, alfalfa butterflyColias euxanthe C. & R. Felder, 1865 – Puno clouded yellowColias felderi Grum-Grshimailo, 1891Colias fieldii Ménétriés, 1855Colias flaveola Blanchard, 1852 – flaveola clouded yellowColias gigantea Strecker, 1900 – great sulphurColias grumi Alpheraky, 1897Colias harfordii W. H. Edwards, 1877 – Harford's sulphurColias hecla Lefèbvre, 1836 – northern clouded yellow, Greenland sulphur, or hecla sulphur Colias heos Colias hofmannorum Eckweiler, 2000Colias hyale – pale clouded yellowColias hyperborea Grum-Grshimailo, 1899Colias interior Scudder, 1862 – pink-edged sulphurColias johanseni Troubridge & Philip, 1990 – Johansen's sulphurColias krauthii Klots, 1935Colias lada Grum-Grshimailo, 1891Colias ladakensis Felder & Felder, 1865 – Ladakh clouded yellowColias leechi Grum-Grshimailio, 1893Colias lesbia – Lesbia clouded yellowColias libanotica Lederer, 1858 Colias marcopolo Grum-Grshimailo, 1888Colias marnoana Rogenhofer, 1884Colias meadii W. H. Edwards, 1871 – Mead's sulphurColias montium Oberthür, 1886Colias mukana Berger, 1981Colias myrmidone – Danube clouded yellowColias nastes Boisduval, 1834 – Labrador sulphurColias nebulosa Oberthür, 1894Colias nilagiriensis Felder, C & R Felder, 1859Colias nina Fawcett, 1904 – Fawcett's clouded yellowColias occidentalis Scudder, 1862 – western sulphur or golden sulfurColias palaeno – moorland clouded yellow, Arctic sulphur, palaeno sulphur or pale Arctic clouded yellowColias pelidne Boisduval & Le Conte, 1829 – blueberry sulphur or pelidne sulphurColias phicomone – mountain clouded yellowColias philodice Godart, 1819 – common sulphur, clouded sulphurColias ponteni Wallengren, 1860Colias pseudochristina Ferris, 1989Colias regia Grum-Grshimailo, 1887Colias romanovi Grum-Grshimailo, 1885Colias sagartia Lederer, 1869Colias scudderii Reakirt, 1865 – willow sulphurColias shahfuladi Clench & Shoumatoff, 1956Colias sieversi Grum-Grshimailo, 1887Colias sifanica Grum-Grshimailo, 1891Colias staudingeri Alphéraky, 1881Colias stoliczkana Moore, 1882 – orange clouded yellowColias tamerlana Staudinger, 1897Colias thisoa Ménétriés, 1832Colias thrasibulus Fruhstorfer, 1908 – lemon clouded yellowColias thula Hovanitz, 1955 – Thula sulphurColias tibetana Riley, 1922Colias tyche – pale Arctic clouded yellow, Arctic green sulphur, or Booth's sulphurColias viluiensis Colias wanda Grum-Grshimaïlo, 1907Colias wiskotti Staudinger, 1882
Distinguishing characteristics
Colias are usually some shade of yellow, orange or white. Their uppersides feature black borders. They always perch with wings closed, but upperside pattern may be seen faintly through the wing, or glimpsed in flight.